Newswise — The reclassification of a woodland grass as two distinct species has created further botanical questions. One of these species is considered imperiled and in need of protection in some areas of the United States. However, that same species has recently been found rapidly spreading into mid-Atlantic states where previously only its sister species was known. Could the plant species have been misidentified?
An article in the current issue of the journal Castanea presents new discoveries of Diarrhena obovata in mid-Atlantic states where they were previously only rarely seen. Both D. obovata and D. americana are large, striking woodland grasses, with obovata originally considered a variety of D. Americana.
In 1991, morphological differences between the two were noted, and D. obovata was proposed as a separate species. The two species occupy different regions of the United States, with D. obovata found predominantly in the Mississippi and Missouri River drainages of the upper Midwest, and D. americana favoring the Ohio River basin and parts of the Ozarks.
Additionally, D. obovata has a hollow endosperm, which might facilitate floating and water transport of seeds, leading it to spread to new areas. This may be why this species has recently been discovered, in rapidly increasing numbers, along the Potomac River in Maryland and Virginia.
Because D. obovata was formerly classified as D. americana, past database records and literature may contain erroneous identifications of the species. This brings into question which species has long thrived in the area and whether new sightings can be identified as a rare find or an aggressive invading force.
The author notes that it is unlikely that D. obovata has simply been overlooked in the past; therefore, its rapid expansion and new abundance could signal a pattern. Locations where the species was considered in danger should re-evaluate its conservation status as similar patterns of expansion may be taking place elsewhere.
Full text of the article, “Diarrhena obovata in the Potomac River Watershed: A New Invader?” Castanea, Vol. 77, No. 2, June 2012, is available at http://www.castaneajournal.org/
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About Castanea Castanea is the journal of the Southern Appalachian Botanical Society and publishes articles relating to all aspects of botany in the entire eastern United States and adjoining areas. The Southern Appalachians—the nonglaciated mountainous areas of Alabama, Georgia, South Carolina, North Carolina, Tennessee, Kentucky, Virginia, West Virginia, Maryland, Pennsylvania, and southwestern New York—form an evolutionary center for native plant diversity for the northern temperate regions of the world. The society dates to 1935 and serves all persons interested in the botany of the Southern Appalachian Mountains. The journal encourages submissions of scientific papers dealing with basic research in any field of plant biology, systematics, floristics, ecology, physiology, and biochemistry. For more information about the journal or society, please visit: http://www.sabs.appstate.edu.
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